Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$104.94	3.588%	$108.7052	$108.71	$108.70	$108.70
Purchase #2	$164.39	13.477%	$186.5448	$186.54	$186.55	$186.50
Purchase #3	$111.85	4.107%	$116.4437	$116.44	$116.45	$116.40
Purchase #4	$82.77	8.655%	$89.9337	$89.93	$89.95	$89.90
Purchase #5	$67.45	3.424%	$69.7595	$69.76	$69.75	$69.80
Purchase #6	$58.78	9.761%	$64.5175	$64.52	$64.50	$64.50
Purchase #7	$75.47	6.600%	$80.451	$80.45	$80.45	$80.50
7 purchase totals =	$665.65		$716.3554	$716.35	$716.35	$716.30